Online Newsletter

Excerpted from our print newsletter. See the printed newsletter for detailed
Field Trip directions and reports, for phone and addresses for yard visits and
additional articles. Join now to obtain
the benefits of full membership!

UPCOMING MEETING IN DADE COUNTY

Stars of the Wildflower World: A Look at the Asteraceae. Speaker: Chuck
McCartney.

After the orchid family, there are probably more species of asters, daisies
and their kin in the family Asteraceae than any other group of vascular
plants, with estimates of 23,000 species worldwide. More than 400 species
are reported for Florida, with 130 reported for Miami-Dade County, 57 for
the Keys, 43 for mainland Monroe County, and 97 for Broward County. Chuck
McCartney, wildflower enthusiast and FNPS member, will share a look at what
makes the Aster family distinctive within the plant world and illustrate
these traits with color slides, concentrating on the species native to southeastern
Florida.

Thanks in advance to refreshment donors Carol Farber (drinks and ice) and
Barbara McAdam, Lee and Scott Massey, Jeff Blakley, Gail Romero (snacks).
Everyone is invited to add to the refreshment table or bring a native plant
for the raffle or auction.

October 23 program. Chris Bergh, Land Conservation Program Manager
for The Nature Conservancy's Florida Keys program: "Florida Keys Natural
Areas; Acquisition and Management for Biological Diversity". (Chris will
lead our November field trip.)

UPCOMING FIELD TRIPS (DADE)

Field trips are for the study of plants and enjoyment of nature by
FNPS members (Dade and Keys) and their invited guests. Collecting is not
permitted. Please join today
so that you can enjoy all the benefits of membership!

Sunday Sept. 30, Everglades National Park. We will look for flowering
members of the aster family (see Sept. meeting) and other early autumn
wildflowers along a fire road that runs along the north rim of Long Pine
Key, where the pine rocklands meet the rocky glades.

ACTIVITIES IN THE KEYS

Note: All Dade Chapter members are welcome at all chapter
activities. For more information about those planned by the Keys Activities
Committee, please call Jim Duquesnel at John Pennekamp Coral Reef State
Park, 305-451-1202.

Meeting: Wednesday, Sept. 19, at John Pennekamp Coral Reef State
Park. Roger Hammer will present a slide program of some of the 306 plants
in his upcoming field guide for wildflowers of the historic Everglades region.
Roger is the Park Naturalist at Castellow Hammock Nature Center in Homestead
and has worked for Miami-Dade County's Parks and Recreation Department since
1977. There will be the usual native plant raffle and refreshments after
the meeting. Anyone donating a raffle plant will receive a free raffle ticket
(home-baked cookies earn a hug from Jim).

The park entrance will open (no charge) at 6:45PM and close promptly
at 7:30PM, so please arrive on time. A plant identification workshop
begins at 7PM (bring a cutting of a mystery plant that includes several
leaves and, if possible, fruit or flowers). The meeting begins at 7:30 and
the program by 7:45.

Field trip: Saturday, Sept. 22. Crane Point Hammock. Leader:
Roland Fisch, Professor at Florida Keys Community College Marathon Campus,
teaching Keys ecology and botany since 1976. Crane Point's museum, outdoor
exhibits, and trails offer some of the very finest environmental education
opportunities in the Keys. The hammock is a wonderful place to learn the
native Keys palms and other middle Keys species.

CHAPTER NEWS AND NEEDS

VOLUNTEERS are needed for our next Everglades National Park Visitors
Center landscaping project workday, Saturday, September 15, 9:00 - noon.
We will call everyone on the volunteer list. Please call Carrie (305-661-9023)
if you plan to attend or if you would like to be added to the master list
of volunteers. We will mostly do pruning, weeding, and mulching when we
arent admiring how nice the project looks after rainfall and a very
productive growing season. Please be sure to bring pruning tools, gloves,
hand trowels, shovels, wheelbarrows, and your preferred insect repellant.
If you can help with calling or bringing refreshments, please call Carrie.

SPECIAL PROGRAM: Butterfly and native plant expert Dr. Marc Minno will
present "The Secret Life of Butterflies, Butterfly Love and Life in Your
Garden" at 1 p.m. on October 28 at Fairchild Tropical Garden.
Marc is a biologist with St. Johns River Water Management District, co-author
of four books on butterflies, including Florida Butterfly Gardening,
Butterflies of the Florida Keys, and Butterflies Through Binoculars,
Florida Edition, and former resident of Broward County. This special
program is sponsored by DCFNPS, FTG and others. The program will be followed
by book signing (FTG will sell the books) and a butterfly walk at 3 p.m.
with Dr. Minno and other butterfly experts. The event is free to the public
after admission to the Garden. Members of FNPS (and other sponsoring organizations)
and their guests may enter the Garden free to attend this program. FNPS
members are asked to RSVP to Lynka Woodbury at 305-667-1651, ext. 3427
(just leave a message).

When science teacher Chris Browlow called the Native Plant Society for
help with an empty greenhouse at Lindsey Hopkins Technical Educational
Center, member Jim Solly came to her rescue. Imagine a third-floor,
downtown greenhouse in Miami without shade cloth, impossibly hot and uninviting.
Jim helped make it cool, and now plants and minds are growing nicely there
together. Thank you, Jim -- great job! Ms. Browlow is an enthusiastic and
devoted teacher, and a visit to her classroom is inspiring. She would welcome
other helpers from our group, too. If you are interested, please call Carrie
Cleland (305-661-9023).

On June 30, employees from Bank of America and members of Treemendous
Miami and DCFNPS participated in a workday at the City of Miamis Simpson
Park, along with park director Pat Quintana and one staff member. Although
the Channel Seven news reported "county workers picking up trash", the hard-working
volunteers were actually removing exotic trees and vines invading
the native hammock of this 8-acre park.

OTHER EVENTS AND ANNOUNCEMENTS

Tropical Audubon Society.Plant sale Sept. 22 (9am-5pm)
and 23 (9am-4pm) featuring native plants common to South Florida and
Cuba. Volunteers from DCFNPS are invited to help in sales, check
out and support. No experience necessary! Doc Thomas House, 5530 Sunset
Dr. 305-666-5111. September 18 meeting: "Native Plants of
Cuba and South Florida" at 8pm, social at 7:30. Plant walks
led by Rock Cohen (please make reservation at 305-666-5111): Oct.21,
Beginning Botany at Matheson Hammock. Nov. 18, Deering Estate at
Cutler.

The Miami based non-profit, The Institute for Regional Conservation
(IRC), has launched a new web site(www.regionalconservation.org),
created by local botanists George D. Gann, Keith A. Bradley,
and Steven W. Woodmansee. Among other things, it features The Floristic
Inventory of South Florida Database. Users can obtain information on native
and naturalized plants of South Florida, and print plant lists for South
Florida parks, counties, and habitats. Contact George or Keith at irc@regionalconservation.org
or (305) 247-6547.

If you work in the environmental field, a Certificate in Environmental
Studies from FIU could improve your credentials or help you get a promotion.
The certificate can be done without formal admission to FIU and involves
taking 6 undergraduate or graduate level course, two each in environmental
science (+lab), environmental social science and environmental electives.
The certificate is appropriate for those who have or are working on a degree.
Call the FIU Environmental Studies office at 348-1930.

INVASIVE EXOTIC PLANTS AND FLORIDAS DILEMMA

by Robert F. Doren

Introduced species have become a significant component of human-caused
global environmental change. Even though this fact has been understood for
some time, most people, even many scientists have failed to recognize or
appreciated the seriousness and potential magnitude of the issue. Biological
invaders are capable of altering ecosystem structure and function. The long-term
consequences of global ecological alterations in disturbance regimes, nutrient
dynamics, soil and water chemistry, changes in species dominance, community
composition and structure and recruitment, evapotranspiration, erosion,
soil formation, microclimate, competition, etc. are basically unknown.

The wholesale and uncontrolled movement of biological organisms by humans
has essentially eliminated the natural biogeographic barriers that originally
created and sustained the major floral and faunal regions of earth and are
obscuring the distinctiveness of the earths biota. While many of these
plants and animals are considered essential to human health and welfare
and are not regarded as threats to biodiversity, they are often a reflection
of other human caused change such as land development, which also threatens
biodiversity. Some non-indigenous species have caused enormous economic
losses, especially in agriculture. Some species affect the structure and
function of ecosystems or the preservation or restoration of native biological
diversity. While economic costs may be able to be documented and cost-risk
analyses for these species may be possible (although little has actually
been done in this regard), the loss of natural ecosystems and native biodiversity
is seldom measurable in economic terms and sometimes considered an unfortunate
byproduct of economic growth.

Humans affect bioinvasion by eliminating the natural barriers to species
movement. Bioinvasion reduces biodiversity through direct loss, extirpation
or extinction of species and through introduction of pests and diseases.

THE ECOLOGY OF INVASION

Why Do Some Species Seem More Invasive Than Others? Why Do Some Ecosystems
Seem More Invasible Than Others? What Contributions Can the Current Science
Provide Toward Understanding the Ecology, the Risk, the Prediction, and
the Management of Invasion Events?

Recent research has begun to focus on the fundamental questions of invasion
ecology, such as "what makes some species more invasive than others?" or
"what makes some ecosystems more invasible than others?" While some useful
predictive information is becoming available for individual species that
are the focus of research projects, useful generalizations applicable to
species characteristics overall or ecosystem properties have not developed
because sufficient quantitative studies are not currently available.

Several theories have been developed from the available science related
to what is generally known about the characteristics of invaders and invaded
ecosystems, and the more decided theories developed from specific ecological
studies.

THE PRINCIPAL THEORIES INCLUDE:

Alteration of ecosystem processes theory.

Invasive species that are capable of altering ecosystem processes or characteristics
are generally thought to be the most serious of invaders and are likely
to have the most dramatic effects on ecosystems. They often differ in life
form from native species, and usually cause change either by creating new
habitat or modifying existing habitat. Alteration of ecological factors
such as hydrology, biogeochemistry, stand structure, resource utilization
and competition are well documented in the literature, and the number of
invasive species capable of altering ecosystem functions and properties
is probably much higher than previously thought.

Disturbance creates gaps theory.

Disturbance is often attributed to enhancement of invasion especially
in "island-like" areas such as south Florida in particular where either
natural disturbance is prevalent or where significant and widespread human
alteration of the natural system has occurred. However there are many examples
of exotic species invading undisturbed habitats and out competing native
species.

Open-niche theory.

Initially it was thought that if evolution and species migration filled
all a plant communities niches that community was considered
species-saturated and was impervious to invasion by exotic species.
The scientific evidence related to this concept is inconsistent at best,
and more recent research suggests that higher native species richness does
not impart resistance to exotic species invasion and some research has even
shown a positive correlation of exotic species invasion with high native
diversity.

Lack of predators and pathogens theory.

This theory presumes that introduced species become invasive because they
are introduced without their natural pests and diseases and with an assumed
concomitant reduction in competition. Some species are reported to grow
and reproduce more robustly in the absence of predators, indicating that
predator-free exotic species may enjoy an advantage over native species,
but the lack of predators is not always associated with invasiveness. However,
the lack of predators is a key concept in the rationale for biological control.

Faster reproductive potential theory.

Many invasive species show either a rapid vegetative growth rate compared
to native homologues. Several species in Florida (such as hydrilla and water
hyacinth) are documented to be able to reproduce much faster that the native
plants in the same habitat. This theory is closely allied with following
concept relating to the questions of poor adaptation in native species versus
better adaptation in exotic species.

Poor adaptation in native species theory.

It is unclear whether some native species in their native ecosystem are
truly less well adapted or tolerant, or if exotic species are simply better
able to utilize existing resources or take advantage of reproductive opportunities
(Also see previous theory on faster reproductive potential). Research indicates
that the later two concepts certainly apply in many well documented instances,
and that invasive species capable of altering ecosystem properties may also
create a relatively novel environment to which the native species may no
longer be adapted.

Availability increases invasibility theory.

There is convincing evidence that the more available a species is the
greater the opportunity for eventual establishment of self-sustaining populations.
The increase in availability of new species over time, and the repeated
availability of existing species also appears to increase the absolute invasion
rate. People are the major cause of species homogenization.

THE BASICS OF BIOINVASION

Most if not all of the exotic species that become invasive share many
traits that help account for their invasive properties. The theories that
endeavor to explain how and why these species are able to become invasive
overlap in many instances, and most species share characteristics of invasiveness
that includes behavior, genetics, physiology, and demography.

How well do these theories predict species invasiveness or ecosystem invasibility?
Unfortunately science currently offers no adequate solutions to this vexing
problem. Invasion characteristics of individual species may be predictable
using biological characters where sufficient data exist. Broader generalizations
are usually limited to plant physiology, species behavior, genetics or demography
of single species, or rarely congeneric species.

Invasive species are the second biggest cause of the loss of global biodiversity
after habitat loss. Bioinvasion is here to stay and will only get worse
if we continue to deal with the problems of exotic species in a piecemeal
and parochial fashion. The message is loud and clearwe must act cooperatively,
collectively, and decisivelyif we are to halt the inevitable loss
of our natural environment and other natural resources to non-native invasive
species. Business as usual has not and will not work.

Why are invasive exotic plants so widespread and numerous?

Documented introductions of plants into Florida have been occurring for
over 200 years, and the numbers of introductions have increased over this
period. Over 25,000 exotic species of plants have been introduced into Florida.
Accidental introductions have been growing as a consequence of increased
commerce and tourism. The more often a species is imported and made more
available, the greater chance it will become invasive, and the more different
species introduced the greater the chance that one will become invasive.

Why are invasive exotic plants considered undesirable?

Invasive exotic plants cause substantial economic losses, reductions in
agricultural production, and significant direct control costs. Billions
of dollars are lost each year in the US. Millions of hectares of natural
areas are infested with exotic plants with a concomitant loss of native
species. Hundreds of rare and endangered species and rare habitats are in
jeopardy from them.

How frequently do exotic species establish self-sustaining populations
and do they all become invasive?

Approximately 10% of introduced species establish reproducing populations
and approximately 10% of those become invasive. However, even a single species
may cause severe ecological damage and substantial economic losses. Increased
availability of exotic species enhances invasion potential and may accelerate
invasion rates. Continued human modification of natural habitats provides
additional opportunities for exotic species to become established.

Why do we still introduce exotic plants if some of them can cause
so much harm?

Exotic organisms are introduced for economic and social benefit. The ecological
and social costs of invasive exotics have been largely ignored and been
borne by the general public. Both rates and kinds of introductions have
fluctuated widely in response to social, political and technological factors.
Commercial trade of living organisms in Florida has grown, increasing the
likelihood of additional plants becoming invasive. Plants are not viewed
as pests by the current US regulatory and port-interdiction programs.

Whats needed to be able to identify species and predict their
potential for invasion?

Scientists are generally able to provide quantitative predictions of invasiveness
for individual species where sufficient studies are available. Quantitative
predictions of invasiveness for groups of similar plants or congeners, or
of ecosystems or plant communities or even regions are more qualitative
and therefore less reliable. However, useful systems of prediction and risk-assessment
for individual species are being successfully used. A risk-assessment system
to evaluate existing and forthcoming species, and a comprehensive invasive
species information scheme are needed for Florida and the US.

Whats needed to prioritize and manage "high-risk" species?

Accurate and timely identification of species, comprehensive and user-friendly
information are essential for helping identify, locate, prioritize and manage
invasive plants. A coherent information system and consistent assessment
techniques to determine distribution need to be developed for Florida. A
national "Early-Warning" information system is being considered. Objective
science-based methods for assessing species risk and evaluating control
success need to be developed and employed.

Where are the plants and whats influencing their distribution?

All regions of Florida and all its ecosystems have populations of naturalized
exotics. There are local and regional differences in impacts, in total numbers
of species present, and acres infested. South Florida and the Tampa Bay
area, have more species and acres of invasive exotic plants than other areas
of Florida. Disturbed natural areas, proximity to major points of import,
increasing commercial availability of exotics, growing human population
and migration, and increasing urbanization probably accounts for the higher
numbers of exotics in these two regions.

How many exotic plants are in Florida and how many of them are considered
invasive?

1,180 exotic plant species are documented as naturalized in Florida. The
Florida Exotic Pest Plant Council has assessed their impacts and invasiveness
in natural areas and has identified 125 as serious threats to natural areas.
Of those, 65 are considered to be extremely serious and highly disruptive
to native plant communities. The report being prepared includes those 65
and giant salvinia as the priority species.

How much do we actually know about exotic species and their distributions?

Generalized distributions, usually from herbarium specimens or routine
sightings, are available for the 66 most invasive species and a few others.
Detailed distribution maps are available for only four species and only
for part of their Florida range, although individual sites, such as parks,
may produce local maps of exotic locations as part of a site- or species-focused
control program. Generalized distributions can be evaluated using the county
sightings surveys (see Figure). Information on the natural history and biology
is generally inadequate for the majority of species. The information gap
for exotic plants is enormous and hinders both species-focused and ecosystem-level
management efforts.

Dr. Robert Doren is a member of the Noxious Exotic Weed Task Team of
the Everglades Restoration Program. A later Tillandsia will contain
information on obtaining a copy of the teams final report, which will
be available this fall.]

The Dade Chapter Florida Native Plant Society is a 501(c)3 nonprofit organization
dedicated to the understanding and preservation of Floridas native
flora and natural areas, and promoting native plants in landscapes.

The chapter includes residents of Miami-Dade County and the Keys. Meetings
in Miami-Dade County are on the 4th Tuesday of each month except
June, August and December at Fairchild Tropical Garden and are free and
open to the public. In June, members and their guests are invited to an
evening garden tour on the 4th Tuesday. Meetings in the Keys
are held on a varying schedule of dates and locations from Key Largo to
Key West. The basic FNPS membership (state and chapter) is $25 per year.
Please contact DCFNPS for a membership application.

Please send articles, announcements of local activities and news of interest
to the Dade Chapter PO Box or email to the editor (above) by the 15th
of each month to be considered for publication the following month.